IPv6 addresses "piling up" in 5268AC DNS

Pace 5268 - I have IPv6 support "on" in my home network - and have "Prefix delegation" and "Address Assignment" both enabled.

The trouble is with IPv6 "SLAAC" addresses - these are all registered with DNS and *never* seem to go away - even after being deprecated and then removed from the v6 interface.

Additionally every time I reboot - SLAAC auto configures a new address and registers it with DNS - but the old address remains as well.  This causes problems with fileserver access and ssh to Linux hosts - ssh has to wait until all the expired, old, deprecated and now invalid addresses are tried and timed out before it successfully connects.

Given that DNS and DHCP aren't really configurable to any degree in the 5268, what can be done to remove old addresses and/or otherwise mitigate this behavior?  It drives me nuts.  A factory reset of the RG clears things out, but that's not a terribly practical thing to have to do often to get rid of stale IPv6 addresses in the local DNS server.

Thanks!